Searchable encryption allows one to store encrypted documents on a
remote honest-but-curious server, and query that data at the
server itself without requiring the documents to be decrypted prior
to searching. This not only protects the data from the prying eyes
of the server, but can also reduce the communication overhead
between the server and the user and local processing at the latter.
Previous research in searchable encryption have investigated exact
match search on keywords and boolean expression search on
keywords. In this work, we first propose a novel secure and
efficient multi-keyword similarity searchable encryption (MKSim)
that returns the matching data items in a ranked order manner.
Unlike many existing schemes, our search complexity is sublinear to
the total number of documents that contain the queried set of
keywords. Our theoretical analysis demonstrates that the proposed
scheme is provably secure against adaptive chosen-keyword attacks,
the strongest form of security sought in searchable encryption.
Next, we develop a proof-of-concept prototype that we use for
experimentation on a large-scale real-world dataset and evaluate the
efficiency and scalability of our solution. Finally, we extend the
MKSim protocol to the multi-user setting in which the data owner
wishes to provide selective access to his encrypted document corpus
to more than one user.